1. Field of the Invention
The invention relates to a radiation-emitting semiconductor component having a semiconductor body, which has an active zone. The semiconductor body is electrically contact-connected and provided with a mirror.
2. Background of the Invention
In the production of light-emitting diode chips based on GaN, there is the fundamental problem that the maximum achievable electrical conductivity of p-doped layers, in particular of p-doped GaN or AlGaN layers, does not suffice for achieving a current expansion over the entire lateral cross section of the chip using a conventional front-side contact metallization known from light-emitting diode chips of other material systems (such a metallizatiion covers only a fraction of the front side for the purpose of coupling out the highest possible amount of radiation).
Growing the p-conducting layer onto an electrically conductive substrate, which would enable current to be impressed over the entire lateral cross section of the p-conducting layer, does not lead to an economically tenable result. The reasons for this can be explained as follows. Firstly, the production of electrically conductive lattice-matched substrates (e.g. GaN substrates) for the growth of GaN-based layers is associated with a high technical outlay; secondly, growing p-doped GaN-based layers onto non-lattice-matched substrates that are suitable for undoped and n-doped GaN compounds does not lead to a crystal quality that is adequate for a light-emitting diode.
In a known approach for combating the problem mentioned above, that side of the p-conducting layer which is remote from the substrate has applied to it, over the whole area, a contact layer which is transmissive to the radiation or an additional electrically readily conductive layer for current expansion, which is provided with a bonding contact.
However, the first-mentioned proposal is associated with the disadvantage that a considerable part of the radiation is absorbed in the contact layer. The second-mentioned proposal requires an additional process step, which significantly increases the manufacturing outlay.
The document DE 100 26 254 A1 discloses a component of the type mentioned in the introduction in which a whole-area contact connection in the form of a silver layer is applied on a semiconductor chip. In this case, in addition to the electrical contact with respect to the light-emitting diode chip, the said silver layer also functions as a reflector for the radiation radiated from the active zone of the chip.
Although the silver layer in the known component forms an ohmic contact which is distinguished by a relatively low resistance compared with a Schottky contact that possibly occurs as well, the contact resistance is nevertheless still too high for many applications.